1. Field of the Invention
The present invention relates to a battery charger for a cellular phone, and more particularly, to a battery charger for a cellular phone, having a speaker which can play music to a listener and enable a telephone conversation in a speaker phone mode during charging the cellular phone.
2. Background of the Related Art
Generally, a battery charger for a cellular phone charges a battery through a connection terminal at the rear of the battery in a state that the battery is only inserted into the battery charger or the cellular phone having the battery is inserted into the battery charger.
FIG. 1 is a perspective view illustrating a related art battery charger for a cellular phone, FIG. 2 is a front view illustrating a related art battery charger into which a cellular phone is inserted, FIG. 3 shows a side view and a rear view of a related art battery charger, and FIG. 4 is a block diagram illustrating a related art battery charger for a cellular phone.
As shown in FIG. 1, the related art battery charger for a cellular phone includes a main body 5 provided with a charging terminal 11 to support the cellular phone when the cellular phone in inserted into the main body 5. Accordingly, if the cellular phone is inserted into the battery charger, a charging terminal 9 of a battery is connected with the charging terminal 11 of the battery charger to charge the battery of the cellular phone as shown in FIGS. 2 and 3.
Referring to FIG. 4, the related art battery charger for a cellular phone includes a filter 20 for eliminating noise of an externally input commercial alternating current voltage of 100-220V, a rectifying and sudden current restricting circuit 22 for converting the alternating current voltage having no noise into a direct current voltage and protecting an internal circuit from sudden variation of voltage and current, a switching and over current protecting circuit 24 for switching the direct current voltage output from the rectifying and sudden current restricting circuit 22 and preventing flow of the over current from occurring, a rectifying circuit 26 for rectifying again the voltage output from the switching and over current protecting circuit 24 to supply more stable direct current voltage, a feedback circuit 30 and a constant voltage integrated circuit 32 for sensing the output voltage of the rectifying circuit 26, and a microcomputer 38 and an output adjusting circuit 34 for controlling the operation of the battery charger.
The operation of the aforementioned battery charger for a cellular phone will now be described.
An external commercial power source becomes a direct current voltage state through the filter 20 and the rectifying and sudden current restricting circuit 22. Thus, the direct current voltage is output through the switching over current protecting circuit 24. The direct current voltage is rectified again by the rectifying circuit 26 so as to be supplied to the battery of the cellular phone as a stable direct current voltage, thereby charging the battery.
The microcomputer 38 senses an output terminal of the rectifying circuit 26 through the feedback circuit 30 and the constant voltage integrated circuit 32. The microcomputer 38 also controls the direct current voltage supplied to the battery through the output adjusting circuit 34, thereby outputting a constant voltage.
Furthermore, the microcomputer 38 senses a temperature of the battery so that the battery is charged only at a constant temperature. The microcomputer 38 also informs a user through a light emitting diode (LED) whether the battery is charging.
However, the related art battery charger for a cellular phone has a drawback in that it is only used for charging the battery of the cellular phone. Accordingly, it is impossible to listen to music during charging the battery of the cellular phone in even case that the cellular phone is designed to play MP3 music. Since it is possible to listen to music in only a standby state of the cellular phone after charging the battery, the battery is consumed quickly, thereby reducing call/standby time.